Most chronic respiratory and nasal diseases, as well as some systemic diseases are treated with inhaled medications. However, a problem with giving medications via inhalers is that patients often do not take their medication as directed. Non-adherence to medication regimes refers to missing doses of medication, incorrect technique when using the inhaler and potentially over medicating. Non-adherence is a major problem rooted in a lack of understanding about medication and a misunderstanding of directions for use. For inhaled medication, adherence involves both using the inhaler at the correct time of day (temporal adherence) and in the correct manner (technique adherence). Rates of non-adherence amongst asthma patients alone range from 30% to 70%. The detection of when and how an inhaler is used by analysing acoustic recordings of inhaler usage can provide evidence about patients' adherence to their inhaled medication regime. Manually listening to acoustic recordings of inhaler usage to assess adherence is a tedious and time consuming process and thus a device or system which can automatically and accurately carry out this task would be of great value.
There are a number of challenges associated with analysing patient inhaler technique through the use of acoustics in uncontrolled environments. Often great quantities of artefacts are generated by the patient or the background environment in which the patient uses their inhaler. In many cases it has been found that patients unintentionally exhale into the mouthpiece of an inhaler, dispersing some or even all of the medication. There are many systems that attempt to use acoustic information to analyse flow rates in terms of inhaler performance.
One such system is disclosed by UK patent publication number GB 2 395 437, assigned to Profile Respiratory Systems, that discloses a system which employs sensors to identify sounds in the operation of the device and primarily associated with investigating flow rates in terms of inhaler performance, however the system does not effectively identify errors in inhaler operation.
Another system is disclosed by PCT patent publication number WO2011/135353, assigned to Sagentia Limited, which discloses a drug delivery device that includes sensors and processing circuitry that can detect operating events, such as flow rates and drug delivery, in various types of inhalers, such as dry powder inhalers, metered dose inhalers, nasal inhalers and nebulisers. The information determined by the processing circuitry can be used to provide feedback to the user or can be stored or transmitted for subsequent analysis. However a problem with this approach is that errors in technique are not identified. After manually classifying several hundred audio recordings of inhaler use, from a wide range of people, it is evident that there are a large number and variety of possible user technique errors. The Sagentia product identifies if the peak inhalation flow profile, as mandated by the manufacturers, is achieved. However if the patient has exhaled into the inhaler before inhalation the dose of the drug available will be reduced, potentially resulting in a missed dose. Exhalations into the device can disperse the drug and introduce a source of humidity to the inhaler. The hydrotropic nature of the drug means that it is likely to combine with the water vapour and clump in the device. This can lead to over dosing in subsequent inhalations. Other user errors include not holding one's breath for the required duration after an inhalation and improper inhalations such as short repeated inhalations instead of one long continuous inhalation.
Other systems in the art include WO2011/083377, assigned to Philips Electronics; EP 0 387 222, Draco AB; and US2011/290240, Meyer Adam et al, that identify one technique error, namely flow rate to achieve correct flow profile, however these systems inherently suffer from the same problems described above.
It is therefore desirable to provide an automatic detection system and method which is able to identify the full drug protocol, or lack of, when using an inhaler. This includes, recording the number doses of medication taken, the timing of these doses and the adherence to the prescribed usage protocol for that inhaler.
It is an object of the invention to provide a device which can record pertinent acoustic information surrounding inhaler use and one that provides valuable information regarding patients' adherence to their medication.